Reduced terminal power consumption via use of active hold state

ABSTRACT

An access terminal (AT) in a cellular communication system is configured to operate in an active hold (AH) state, a transitional state between traffic and dormant states. The AT applies power to its transmit chain with a low duty cycle while in the AH state, conserving battery power. To improve robustness of the communications, the radio network may power control the AT to a higher level relative to the power control level of the AT in the traffic state. Transition from the traffic state to the AH state may be initiated after a brief period of inactivity on the reverse link. The AT may remain in the AH state while receiving forward link payload data. Transmission of a reverse link payload packet in the AH state may initiate transition to the traffic state. A prolonged period of inactivity may initiate a transition from the AH state to the dormant state.

CLAIM OF PRIORITY UNDER 35 U.S.C. §119

The present Application for Patent claims priority to U.S. ProvisionalPatent Application Ser. No. 60/775,443, entitled “Wireless CommunicationSystem and Method,” filed on Feb. 21, 2006; the present Application forPatent also claims priority to U.S. Provisional Patent Application Ser.No. 60/775,693, entitled “DO Communication System and Method,” filed onFeb. 21, 2006. Each of these Provisional Patent Applications is assignedto the assignee of the present Application and is expressly incorporatedby reference as if fully set forth herein, including all figures,tables, and claims.

BACKGROUND

1. Field

The present invention relates generally to telecommunications, and, morespecifically, the invention relates to wireless communication systemsand cellular communication systems.

2. Background

A modem communication system is expected to provide reliable datatransmission for a variety of applications, such as voice and dataapplications. In a point-to-multipoint communications context, knowncommunication systems are based on frequency division multiple access(FDMA), time division multiple access (TDMA), code division multipleaccess (CDMA), and perhaps other multiple access communication schemes.

A CDMA system may be designed to support one or more CDMA standards,such as (1) the “TIA/EIA-95 Mobile Station-Base Station CompatibilityStandard for Dual-Mode Wideband Spread Spectrum Cellular System” (thisstandard with its enhanced revisions A and B may be referred to as the“IS-95 standard”), (2) the “TIA/EIA-98-C Recommended Minimum Standardfor Dual-Mode Wideband Spread Spectrum Cellular Mobile Station” (the“IS-98 standard”), (3) the standard sponsored by a consortium named “3rdGeneration Partnership Project” (3GPP) and embodied in a set ofdocuments known as the “W-CDMA standard,” (4) the standard sponsored bya consortium named “3rd Generation Partnership Project 2” (3GPP2) andembodied in a set of documents including “TR-45.5 Physical LayerStandard for cdma2000 Spread Spectrum Systems,” the “C.S0005-A UpperLayer (Layer 3) Signaling Standard for cdma2000 Spread SpectrumSystems,” and the “TIA/EIA/IS-856 cdma2000 High Rate Packet Data AirInterface Specification” (the “cdma2000 standard” collectively), (5) the1xEV-DO standard, and (6) certain other standards. The standardsexpressly listed above are incorporated by reference as if fully setforth herein, including annexes, appendices, and other attachments.

Data-only and data-optimized or “DO” cellular communication systems havebeen developed to satisfy the constantly increasing demand for wirelessdata services. As the name implies, DO systems are optimized for datatransmission (as opposed to voice transmission), and in particular suchsystems are optimized for downlink data transmission. Data-optimizedsystems need not exclude uplink data transmission, or voice transmissionin either direction. It should be noted that voice may be transmitted asdata, for example, in the case of voice over internet protocol (VoIP)transmissions.

In wireless networks, an access terminal configured for communicationmay be in a traffic state/mode or in a dormant state/mode. In thetraffic state, air link resources for communication between the accessterminal and the radio network are allocated at the radio network andpowered on at the access terminal. Air link resources at the accessterminal may include, for example, finger resources and channelelements. In the dormant state, the traffic channel is torn down, andair link resources are powered off at the access terminal. Powerrequired for operating these resources is consequently not spent duringthe dormant state, and battery life at the access terminal is extended.Other subsystems of the access terminal may also be powered off or putinto a power saving mode for most of the time during the dormant state;the access terminal then wakes up every so often to listen to the pagingchannel of the wireless system, in order to respond to the incomingpages or communication requests. The duty cycle of such periodic pagingchannel checks is low, to reduce the stand-by power consumption.

For a given battery capacity, power consumption determines the amount oftime that the access terminal can operate without recharging.Conversely, for a specified operating time between recharging thebattery, average power consumption determines the required batterycapacity and, consequently, the size, weight, and cost of the battery.Reducing power consumption of an access terminal is thus quiteimportant.

Because transmissions from a given access terminal are interference fortransmissions from other access terminals, it is also desirable toreduce the duration and/or power levels of such transmissions.

Therefore, there is a need in the art for methods and apparatus thatwould reduce power consumption and interference of access terminals.There is also a need in the art for methods and apparatus for reducingpower consumption and interference of the access terminals withoutexcessively compromising performance characteristics of the accessterminals and of the radio networks with which the terminalscommunicate. There is a further need for methods of upgradingpreviously-deployed networks to provide for reduced access terminalpower consumption and interference, while at the same time maintainingbackward compatibility with legacy access terminals, and minimizing oreliminating hardware changes to the radio network.

SUMMARY

Embodiments disclosed herein address the above stated needs by providingmethods, apparatus, and machine-readable articles of manufacture forimplementing an active hold state in a wireless access terminal, and forcommunicating with the wireless access terminal.

In an embodiment, a wireless access terminal for communicating with abase transceiver station of a radio network includes a receiverconfigured to receive forward link transmissions from the basetransceiver station, a transmitter configured to send reverse linktransmissions to the base transceiver station, a memory storing programcode, and a controller coupled to the receiver, transmitter, and thememory. The controller is configured to execute the program code tocause the wireless access terminal to: (1) initiate a transition from atraffic state to an active hold state in response to absence of reverselink traffic during a first predetermined time period, (2) initiate atransition from the active hold state to the traffic state in responseto presence of reverse link traffic, (3) initiate a transition from theactive hold state to a dormant state in response to absence of forwardlink traffic and reverse link traffic during at least a secondpredetermined period, (4) initiate a transition from the dormant stateto the traffic state in response to presence of reverse link traffic,(5) remain in the active hold state after transitioning into the activehold state during simultaneous presence of forward link traffic andabsence of reverse link traffic (i.e., the forward link traffic ispresent at the same time as reverse link traffic is absent), and (6)power off at least one component of the transmitter in the active holdstate so that duty cycle of said at least one component is less than apredetermined threshold in the active hold state. In aspects, thethreshold may be twenty-five percent of the duty cycle.

In an embodiment, a machine-readable medium comprises instructionsembedded therein. When the instructions are executed by at least oneprocessor of a wireless access terminal for communicating with a basetransceiver station of a radio network, the instructions cause thewireless access terminal to (1) initiate a transition from a trafficstate to an active hold state in response to absence of reverse linktraffic during a first predetermined time period, (2) initiate atransition from the active hold state to the traffic state in responseto presence of reverse link traffic, (3) initiate a transition from theactive hold state to the dormant state in response to absence of forwardlink traffic and reverse link traffic during at least a secondpredetermined period, (4) initiate a transition from the dormant stateto the traffic state in response to presence of reverse link traffic,(5) after transitioning into the active hold state, remain in the activehold state during simultaneous presence of forward link traffic andabsence of reverse link traffic, and (6) in the active hold state, poweroff at least one component of the transmitter so that duty cycle of saidat least one component is less than twenty-five percent in the activehold state.

In an embodiment, a wireless access terminal for communicating with abase transceiver station of a radio network includes a means forreceiving forward link transmissions from the base transceiver station(e.g., a receiver/receiver chain), a means for sending reverse linktransmissions to the base transceiver station (e.g., atransmitter/transmitter chain), a means for storing program code (e.g.,a memory device), and a controller means (e.g., a processor) forexecuting the program code to cause the wireless access terminal toperform a number of steps. The steps include (1) initiating a transitionfrom a traffic state to an active hold state in response to absence ofreverse link traffic during a first predetermined time period, (2)initiating a transition from the active hold state to the traffic statein response to presence of reverse link traffic, (3) initiating atransition from the active hold state to a dormant state in response toabsence of forward link traffic and reverse link traffic during at leasta second predetermined period, (4) initiating a transition from thedormant state to the traffic state in response to presence of reverselink traffic, (5) after transitioning into the active hold state,remaining in the active hold state during simultaneous presence offorward link traffic and absence of reverse link traffic, and (6)powering off at least one component of the transmitter so that dutycycle of said at least one component is less than twenty-five percent inthe active hold state.

In an embodiment, a method is provided for operating a wireless accessterminal communicating with a base transceiver station of a radionetwork. The method includes these steps: (1) initiating a transitionfrom a traffic state to an active hold state in response to absence ofreverse link traffic between the wireless access terminal and the basetransceiver station during a first predetermined time period, (2)initiating a transition from the active hold state to the traffic statein response to presence of reverse link traffic between the wirelessaccess terminal and the base transceiver station, (3) initiating atransition from the active hold state to the dormant state in responseto absence of forward link traffic and reverse link traffic between thewireless access terminal and the base transceiver station during atleast a second predetermined period, (4) initiating a transition fromthe dormant state to the traffic state in response to presence ofreverse link traffic between the wireless access terminal and the basetransceiver station, (5) after transitioning into the active hold state,causing the wireless access terminal to remain in the active hold stateduring simultaneous presence of forward link traffic and absence ofreverse link traffic between the wireless access terminal and the basetransceiver station, and (6) in the active hold state, powering off atleast one component of a transmit chain of the wireless access terminalso that duty cycle of said at least one component is less thantwenty-five percent in the active hold state.

In an embodiment, a method is provided for operating a wireless accessterminal for communicating with a base transceiver station of a radionetwork through a forward link and a reverse link. The method includesthe following steps: (1) step for causing the wireless access terminalto enter a dormant state in response to a period of traffic inactivityon the forward and reverse links between the wireless access terminaland the base transceiver station, (2) step for causing the wirelessaccess device to enter a traffic state in response to traffic activityon the reverse link, and (3) step for causing the wireless accessterminal to enter an active hold state in response to a period oftraffic inactivity on the reverse links. In the method, the step forcausing the wireless access terminal to enter the active hold state isperformed regardless of traffic activity on the forward link, and thewireless access terminal in the active hold state powers on and off atleast a portion of a transmit chain of the wireless access terminal witha duty cycle smaller than twenty-five percent.

In an embodiment, a base transceiver station in a radio network isprovided. The base transceiver station includes a receiver configured toreceive data from a wireless access terminal on a reverse link, atransmitter configured to transmit data to the wireless access terminalon a forward link, and a processor coupled to the receiver and to thetransmitter. The processor is configured to cause the base transceiverstation to perform steps comprising: (1) granting a request from thewireless access terminal to enter an active hold state, wherein thewireless access terminal generates the request in response to a periodof traffic inactivity on the reverse link, and wherein the wirelessaccess terminal decreases feedback update frequency for the forward linkin the active hold state relative to a traffic state, (2) transmittingforward link traffic while the wireless access terminal is in the activehold state, and (3) receiving reverse link traffic in the traffic state.

In an embodiment, a base transceiver station in a radio network includesthe following components: a means for receiving data from a wirelessaccess terminal on a reverse link, a means for transmitting data to thewireless access terminal on a forward link, and a control means forprocessing. The control means is coupled to the receiver and to thetransmitter, and is configured to cause the base transceiver station toperform these steps: (1) granting a request from the wireless accessterminal to enter an active hold state, wherein the wireless accessterminal generates the request in response to a period of trafficinactivity on the reverse link, and wherein the wireless access terminaldecreases feedback update frequency for the forward link while in theactive hold state relative to a traffic state, and (2) transmittingforward link traffic while the wireless access terminal is in the activehold state.

In an embodiment, a method is provided for operating a base transceiverstation in a radio network to control a wireless access terminal. Themethod includes (1) granting a request from the wireless access terminalto enter an active hold state, wherein the wireless access terminalgenerates the request in response to a period of traffic inactivity on areverse link between the wireless access terminal and the basetransceiver station, wherein the wireless access terminal in the activehold state provides feedback for a forward link between the wirelessaccess terminal and the base transceiver station with a first frequency,an wherein the wireless access terminal provides feedback for theforward link in a traffic state with a second frequency, the secondfrequency being greater than the first frequency, and (2) transmittingtraffic on the forward link while the wireless access terminal is in theactive hold state.

In an embodiment, a machine-readable medium includes instructionsembedded therein. When the instructions are executed by at least oneprocessor of a base transceiver station of a radio network, theinstructions cause the base transceiver station to perform the followingoperations: (1) granting a request from a wireless access terminal toenter an active hold state, wherein the wireless access terminalgenerates the request in response to a period of traffic inactivity on areverse link between the wireless access terminal and the basetransceiver station, wherein the wireless access terminal in the activehold state provides feedback for a forward link between the wirelessaccess terminal and the base transceiver station with a first frequency,an wherein the wireless access terminal provides feedback for theforward link in a traffic state with a second frequency, the secondfrequency being greater than the first frequency, and (2) transmittingtraffic on the forward link while the wireless access terminal is in theactive hold state.

These and other embodiments and aspects of the present invention will bebetter understood with reference to the following description, drawings,and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates selected components of a cellular communicationsystem configured in accordance with an embodiment of the presentinvention;

FIG. 2 is a state diagram showing selected states and transitions of anaccess terminal operating in the network of FIG. 1 and configured inaccordance with an embodiment of the present invention;

FIG. 3 is a simplified overview of operation of an access terminal inthe active hold state, in accordance with an embodiment of the presentinvention; and

FIG. 4 illustrates selected steps and decision blocks of a processperformed by an access terminal in the active hold state, in accordancewith an embodiment of the present invention.

DETAILED DESCRIPTION

In this document, the words “embodiment,” “variant,” and similarexpressions are used to refer to particular apparatus, process, orarticle of manufacture, and not necessarily to the same apparatus,process, or article of manufacture. Thus, “one embodiment” (or a similarexpression) used in one place or context can refer to a particularapparatus, process, or article of manufacture; the same or a similarexpression in a different place can refer to a different apparatus,process, or article of manufacture. The expression “alternativeembodiment” and similar phrases are used to indicate one of a number ofdifferent possible embodiments. The number of possible embodiments isnot necessarily limited to two or any other quantity.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any embodiment or variant described hereinas “exemplary” is not necessarily to be construed as preferred oradvantageous over other embodiments or variants. All of the embodimentsand variants described in this description are exemplary embodiments andvariants provided to enable persons skilled in the art to make or usethe invention, and not to limit the scope of legal protection affordedthe invention, which is defined by the claims and their equivalents.

The word “traffic” generally refers to payload or user traffic, such asdata other than air interface control and pilots.

An access terminal, also referred to as AT, subscriber station, userequipment, UE, mobile terminal, or MT, may be mobile or stationary, andmay communicate with one or more base transceiver stations. An accessterminal may be any of a number of types of devices, including but notlimited to PC card, external or internal modem, wireless telephone, andpersonal digital assistant (PDA) with wireless communication capability.An access terminal transmits and receives data packets to or from aradio network controller through one or more base transceiver stations.

Base transceiver stations and base station controllers are parts of anetwork called radio network, RN, access network, and AN. Radio networkmay be a UTRAN or UMTS Terrestrial Radio Access Network. The radionetwork may transport data packets between multiple access terminals.The radio network may be further connected to additional networksoutside the radio network, such as a corporate intranet, the Internet, aconventional public switched telephone network (PSTN), or another radionetwork, and may transport data and voice packets between each accessterminal and such outside networks. Depending on conventions and on thespecific implementation variants, a base transceiver station may bereferred to by other names, such as Node-B, base station system (BSS),or simply base station. Similarly, a base station controller may bereferred to by other names, such as radio network controller, RNC,controller, mobile switching center, or serving GPRS support node.

The scope of the invention extends to these and similar wirelesscommunication system components.

FIG. 1 illustrates selected components of a communication network 100,which includes a radio network controller 110 coupled to wireless basetransceiver stations 120A, 120B, and 120C. The base transceiver stations120 communicate with access terminals 130A, 130B, 130C, and 130D throughcorresponding wireless connections 140A through 140E. Each of thewireless connections 140 represents both a forward link (from the BTS tothe AT, also known as downlink) and a reverse link (from the AT to theBTS, also known as uplink). The radio network controller 110 is coupledto a public switched telephone network 150 through a telephone switch160, and to a packet switched network 170 through a packet data servernode (PDSN) 180. Data interchange between various network elements, suchas the radio network controller 110 and the packet data server node 180,can be implemented using any number of protocols, for example, theInternet Protocol (IP), an asynchronous transfer mode (ATM) protocol,T1, E1, frame relay, and other protocols.

The radio network controller 110 and the base transceiver stations 120may be part of a data-optimized radio network, such as a 1xEV-DOnetwork. In the illustrated embodiment, the radio network provides bothdata communication services and cellular telephone services to theaccess terminals 130. In alternative embodiments, the radio network mayprovide only data services (including VoIP and similar packetizeddata-based voice communications), or only voice services.

Multiple or even all the access terminals 130 may be in the same cell orsite, or each access terminal 130 may be in a separate cell or site.

A typical access terminal, for example, the access terminal 130A,includes receiver circuitry 131, transmitter circuitry 132, encoder 133,decoder 134, equalizer 135, processor 136, and memory device 137. Thereceiver, transmitter, encoder, decoder, and equalizer are configured bythe processor executing program code stored in the memory device. Eachaccess terminal 130 is configured to communicate data using at least onetransmission protocol, such as the wireless packet transmissionprotocols described in the specifications mentioned above. The accessterminals 130 communicate with the base transceiver stations 120 viacommunication channels 140A through 140E, as shown in FIG. 1.

Each of the base transceiver stations 120 includes one or more wirelessreceivers (e.g., receiver 121 of the BTS 120A), one or more wirelesstransmitters (e.g., transmitter 122 of the BTS 120A), radio networkcontroller interface (e.g., interface 123), a memory (e.g. memory 124),a processor (e.g. processor 125), and encoder/decoder circuitry (e.g.,encoder/decoder circuitry 126). A receiver/transmitter pair and othercomponents of each base transceiver station are configured by thestation's processor operating under control of the program code storedin the BTS's memory, to establish forward and reverse links with theaccess terminals 130 in order to send packets to and receive packetsfrom the access terminals 130. In the case of data services, forexample, the base transceiver stations 120 may receive forward link datapackets from the packet switched network 170 through the packet dataserver node 180 and through the radio network controller 110, andtransmit these packets to the access terminals 130. The base transceiverstations 120 may receive reverse link data packets that originate at theaccess terminals 130, and forward these packets to the packet switchednetwork 170 through the radio network controller 110 and the packet dataserver node 180. In the case of telephone (voice) services, the basetransceiver stations 120 may receive forward link data packets from thetelephone network 150 through the telephone switch 160 and through theradio network controller 110, and transmit these packets to the accessterminals 130. Voice packets originating at the access terminals 130 maybe received at the base transceiver stations 120 and forwarded to thetelephone network 150 via the radio network controller 110 and thetelephone switch 160.

In some alternative embodiments, the transmitter, receiver, and othercomponents of each BTS may each have separate processors.

The radio network controller 110 includes one or more interfaces 111 tothe base transceiver stations 120, an interface 112 to the packet dataserver node 180, and an interface 113 to the telephone switch 160. Theinterfaces 111, 112, and 113 operate under control of one or moreprocessors 114 executing program code stored in one or more memorydevices 115.

The network 100 illustrated in FIG. 1 includes one public switchedtelephone network, one packet switched network, one base stationcontroller, three base transceiver stations, and four access terminals.A person skilled in the art would recognize, after perusal of thisdocument, that alternative embodiments in accordance with aspects of theinvention need not be limited to any particular number of thesecomponents. For example, a lesser or a greater number of basetransceiver stations and access terminals may be included in someembodiments. Furthermore, the communication network 100 may connect theaccess terminals 130 to one or more additional communication networks,for example, a second wireless communication network having a number ofwireless access terminals.

As has already been mentioned, a known access terminal configured forcommunication may be in a dormant or traffic state, depending on thestatus of the network traffic between such known access terminal and theradio network. The traffic state corresponds to traffic activity betweenthe radio network and the mobile terminal. For example, an accessterminal may transition from dormant to traffic state in response to avoice call or data communication. The voice call or the datacommunication may be incoming (to the access terminal) or outgoing (fromthe access terminal). Conversely, the access terminal may transitionfrom the traffic state to the dormant state when traffic activity ceasesfor some predetermined period of time. Typically, the radio networkcontrols the transitions between the two states.

Traffic activity may be quite asymmetrical between the radio network andthe access terminal. In other words, considerably more traffic may becommunicated in one direction than in the opposite direction. This isparticularly so for data communication, when downlink traffic flowtypically exceeds uplink traffic flow by a large margin. For example, auser at an access terminal may be downloading a large file for arelatively long period of time, with mostly control information beingcommunicated uplink. The control information may be from various layers,for example, Internet Protocol (IP) acknowledgements, and power control,rate control, and pilot of the physical air link. Similarly, a VoIPconversation may be one-sided, with the user at the access terminalmostly listening or holding the line for long stretches of the time.During such time periods, uplink resources of the access terminalcontinue to be powered on and consequently consuming power, althoughthey are not needed to carry user (payload) data from the accessterminal to the radio network.

In an embodiment, an access terminal 130 (e.g. the access terminal 130A)communicates with a base transceiver station (e.g., BTS 120A) of a radionetwork. The radio network may be, for example, a data-optimized radionetwork such as 1xEV-DO network, a data-only network, or a voice-onlynetwork. The access terminal is configured to be in one of three stateswhile connected to the radio network: (1) traffic state, (2) dormantstate, and (3) active hold (AH) state. The first two states are similaror identical to the conventional traffic and dormant states of an accessterminal, respectively. The active hold state is a transitionalintermediate state between the dormant and traffic states. This stateallows additional reduction in the power consumption of the accessterminal, particularly during prolonged periods of reverse link trafficinactivity that coincide with forward link traffic activity of theaccess terminal.

In the active hold state, certain air link resources are used with a lowduty cycle by the access terminal. For example, channel elements, fingerresources, and other transmit chain components may be powered down (off)on the reverse link side of the access terminal for a substantialpercentage of the time. For example, the duty cycle of the transmitchain may be less than fifty percent, less than twenty-five percent, orless than five percent. In some variants, the access network (e.g., BTS)does not deallocate, deassign, or power off channel elements and fingerresources from serving the access terminal in the active hold state.Moreover, in some variants the radio network does not deallocate anyresources from the access terminal in this state.

FIG. 2 is a state diagram showing transitions between the traffic state210, dormant state 220, and active hold state 230. In the traffic state210, the access terminal 130 is actively communicating with the basetransceiver station 120. A transition 213 from the traffic state 210 tothe active hold state 230 takes place in response to a brief period oftraffic inactivity. (It should be noted that the references to activityand inactivity that cause or initiate the transitions between thetraffic, dormant, and active hold states are references to payloadtraffic activity or inactivity, respectively.) The transition 213 maytake place after a period of reverse link inactivity, and/or after aperiod of both reverse and forward link inactivity. In some embodiments,the transition 213 is initiated after expiration of a reverse link AH(active hold) inactivity timer, or after expiration of a reverse link AHinactivity timer and a forward link AH inactivity timer. (The two timersmay be set to expire after the same or different time periods.)

A transition 231 from the active hold state 230 to the traffic state 210is initiated when traffic activity between the access terminal and theradio network renews. For example, reverse link traffic will initiatethe transition 23 1. In variants where the access terminal enters theactive hold state 230 due to brief inactivity on both reverse andforward links (rather than on the reverse link alone), renewed forwardlink activity may also initiate the transition 231.

A transition 232 from the active hold state 230 to the dormant state 220is initiated in response to another period of traffic inactivity whilein the active hold state 230. The transition 232 may take place after aperiod of inactivity on both the reverse and the forward links. In someembodiments, the transition 232 is initiated after expiration of areverse link dormant inactivity timer and after expiration of a forwardlink dormant inactivity timer. As in the case of the transition 213, thetwo timers may be set to expire after the same or different timeperiods. The transition 232 is therefore initiated after some period ofinactivity on both the reverse and the forward links.

A transition 221 from the dormant state 220 to the traffic state 210 isinitiated in response to presence of reverse link traffic. In someembodiments, the transition 221 may be initiated in response to anytraffic (payload) between the access terminal and the base transceiverstation. In some embodiments, however, a transition 223 from the dormantstate 220 to the active hold state 230 is initiated in response tosolely forward link traffic, while the transition 221 is initiatedwhenever reverse link traffic appears.

The transitions between the different states shown in FIG. 2 may beinitiated by the access terminal, for example, by sending an otherwiseunused (spare) codeword on the reverse rate indicator (RRI) channel. Theuse of a spare RRI codeword is advantageous because it is unlikely to bemistaken for anything else at the radio network. The radio network (theradio network controller 110, for example) then decides whether to grantthe transition requested. The grant may be sent to the access terminalon one of the forward link control channels, for example on theacknowledge (ACK) channel. In effect, the ACK in response to the RRIindicates that the radio network also transitioned the access terminalto the active hold state. Alternatively or additionally, the radionetwork may initiate some of the transitions, by sending an appropriatecontrol message to the access terminal. In specific variants, thetransitions are initiated as follows:

The transition 213 from the traffic state 210 to the active hold state230—Initiated by the access terminal through the RRI channel using aspecial RRI codeword, and granted by the access network through the ACKchannel;

The transition 232 from the active hold state 230 to the dormant state220—Initiated by either the access terminal or the radio network afterprolonged inactivity (at least 2 seconds) of both reverse and forwardlink traffic;

The transition 231 from the active hold state 230 to the traffic state210—Initiated by the access terminal due to a reverse link packet andgranted by the radio network. The special RRI codeword may be used totransition to the active hold state (access terminal may use this toindicate to the radio network that it is attempting to enter the activehold state), and the ACK channel in response to the special RRI codewordmay be the radio network indicating to the access terminal that theaccess terminal is now in the active hold state.

It should be noted that the ACK channel messages may remain the same asin existing systems, but the interpretation of these messages may changewhen the access terminal is in the active hold state. For example, whenthe access terminal in the active hold state sends a reverse linkpacket, the acknowledgement of the packet by the radio network on theACK channel also serves to take the access terminal from the active holdstate to the traffic state.

Let us now turn to the operation in the active hold state, e.g. thestate 230. As has already been discussed, in some variants the accessterminal (e.g., the terminal 130A) can be in this state while receivingforward link payload traffic. In these variants, the access terminal canpower down the transmit chain elements for most of the time, turning thetransmit chain back on when providing downlink feedback information.Because of the low duty cycle of the transmit chain being powered onwhile in the active hold state, as compared to the traffic state,significant power savings may be achieved. In some specific variants,the access terminal powers on its transmit chain to provide feedback(e.g., power control, data rate control, reverse link pilot, data sourcecontrol) to the radio network once every 8 slots, corresponding to about75 Hertz update rate; in other specific variants, the access terminalpowers on its transmit chain once every 16 slots, corresponding to theupdate rate of about 37.5 Hertz. These update rates are two and fourtimes slower, respectively, than the 150 Hertz update rate (once inevery 4 slots in 1xEV-DO revision B) used in the traffic state. Itshould be noted that the invention is not limited to the particularupdate rates, or to the particular ratios between the active hold andtraffic state update rates.

Providing feedback information at a slower rate may make communicationsbetween the access terminal and the radio network less robust,particularly in dynamic environments with fast changing physicalpropagation paths. For example, the physical propagation path betweenthe access terminal and the base transceiver station may deteriorate(fade) faster than the radio network can compensate for by increasingthe power control set point of the access terminal. To counteract thispotential problem, in some variants the radio network increases thepower control set point of the access terminal in the active hold state,relative to the power control set point in the traffic state with thesame signal to noise and interference ratio (SINR). In some specificvariants, the power control set point may be increased by approximately1 dB, 2 dB, 3 dB, or 4 dB. The increase in the power control set pointand the decrease in the update rate may depend on each other and bevariable. For example, the power control set point may be increased by 2dB (over the corresponding set point in traffic state given the sameSINR) every time the update rate is halved (also relative to thecorresponding rate in the traffic state). Furthermore, in some variants,the radio network increases the set point only up to a certain powerlimit. The power limit may be such that the increase of power beyond thelimit would begin to affect power consumption of the access terminal. Inmany access terminals, the total power consumption is essentially thesame (within 0.1 mW, for example) regardless of the actual transmitpower, up until the transmit power reaches the power limit. Therefore,there is little penalty from the power consumption perspective inincreasing the power control set point, as long as the transmit powerdoes not exceed the aforementioned power limit. The power limit may beapproximately 0 dBm, 5 dBm, or 10 dBm. These are of course exemplaryvalues, and the actual power limit may differ.

FIG. 3 is a simplified overview of operation of certain variants in theactive hold state.

FIG. 4 illustrates an exemplary process 400 performed by an accessterminal in the active hold state. At flow point 401, the accessterminal has entered the active hold state due to some period ofinactivity on the reverse link (during which period no payload data hadbeen transmitted from the access terminal to the base transceiverstation serving the access terminal). At step 405, the access terminaldecreases the frequency of providing feedback updates to the basetransceiver station. The base transceiver station may concurrentlyincrease the power control set point of the access terminal.

At decision block 410, the access terminal determines if traffic(payload) activity has renewed on the reverse link. If there is renewedtraffic activity on the reverse link, a transition to the traffic stateis initiated at step 415, and the process 400 ends at flow point 499.

If there is no renewed traffic activity on the reverse link, processflow continues to decision block 420, in which the access terminaldetermines whether the elapsed time since last traffic is greater thansome limit. The limit may be predetermined. If the elapsed time does notexceed the limit, as may be the case when the base transceiver stationcontinues to transmit forward link traffic, process flow returns todecision block 410.

If the elapsed time exceeds the limit, a transition to the dormant stateis initiated in step 425, and the process 400 ends at flow point 499.

Although steps and decisions of various methods may have been describedserially in this disclosure, some of these steps and decisions may beperformed by separate elements in conjunction or in parallel,asynchronously or synchronously, in a pipelined manner, or otherwise.There is no particular requirement that the steps and decisions beperformed in the same order in which this description lists them, exceptwhere explicitly so indicated, otherwise made clear from the context, orinherently required. (It should be noted, however, that in selectedvariants the steps and decisions are performed in the order describedabove.) Furthermore, not every illustrated step and decision may berequired in every embodiment in accordance with the invention, whilesome steps and decisions that have not been specifically illustrated maybe desirable or necessary in some embodiments in accordance with theinvention.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the embodiments disclosed herein may be implemented aselectronic hardware, computer software, or combinations of both. To showclearly this interchangeability of hardware and software, variousillustrative components, blocks, modules, circuits, and steps have beendescribed above generally in terms of their functionality. Whether suchfunctionality is implemented as hardware, software, or combination ofhardware and software depends upon the particular application and designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions should not beinterpreted as causing a departure from the scope of the presentinvention.

The various illustrative logical blocks, modules, and circuits describedin connection with the embodiments disclosed herein may be implementedor performed with a general purpose processor, a digital signalprocessor (DSP), an application specific integrated circuit (ASIC), afield programmable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g. a combination ofa DSP and a microprocessor, a plurality of microprocessors, one or moremicroprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with theembodiments disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such that theprocessor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in an access terminal. Alternatively, theprocessor and the storage medium may reside as discrete components in anaccess terminal.

The previous description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein, but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

1. A wireless access terminal for communicating with a base transceiverstation of a radio network, the wireless access terminal comprising: areceiver configured to receive forward link transmissions from the basetransceiver station; a transmitter configured to send reverse linktransmissions to the base transceiver station; a memory storing programcode; and a controller coupled to the receiver, transmitter, and thememory, wherein the controller is configured to execute the program codeto cause the wireless access terminal to: initiate a transition from atraffic state to an active hold state in response to absence of reverselink traffic during a first predetermined time period, initiate atransition from the active hold state to the traffic state in responseto presence of reverse link traffic, initiate a transition from theactive hold state to a dormant state in response to absence of forwardlink traffic and reverse link traffic during a second predeterminedperiod, initiate a transition from the dormant state to the trafficstate in response to presence of reverse link traffic, remain in theactive hold state after transitioning into the active hold state duringsimultaneous presence of forward link traffic and absence of reverselink traffic, and power off at least one component of the transmitter inthe active hold state so that duty cycle of said at least one componentis less than twenty-five percent in the active hold state.
 2. Thewireless access terminal of claim 1, wherein the controller is furtherconfigured to execute the program code to cause the wireless accessterminal to power on said at least one component of the transmitter forat least a majority of time in the traffic state.
 3. The wireless accessterminal of claim 2, wherein the controller is further configured toexecute the program code to cause the wireless access terminal toprovide feedback to the base transceiver station with a first frequencyin the active hold state, and to provide feedback to the basetransceiver station with a second frequency in the traffic state, thesecond frequency being greater than the first frequency.
 4. The wirelessaccess terminal of claim 3, wherein the second frequency is twice thefirst frequency.
 5. The wireless access terminal of claim 3, wherein thesecond frequency is four time the first frequency.
 6. The wirelessaccess terminal of claim 3, wherein the feedback comprises reverse linkpilot and forward link rate control.
 7. The wireless access terminal ofclaim 2, wherein the controller is further configured to execute theprogram code to cause the wireless access terminal to provide feedbackto the base transceiver station once in eight slots in the active holdstate, and to provide feedback to the base transceiver station once infour slots in the traffic state.
 8. The wireless access terminal ofclaim 2, wherein the controller is further configured to execute theprogram code to cause the wireless access terminal to provide feedbackto the base transceiver station once in sixteen slots in the active holdstate, and to provide feedback to the base transceiver station once infour slots in the traffic state.
 9. The wireless access terminal ofclaim 1, wherein the controller is further configured to execute theprogram code to cause the wireless access terminal to transition fromthe dormant state to the active hold state in response to simultaneouspresence of forward link traffic and absence of reverse link traffic.10. A machine-readable medium comprising instructions, the instructions,when executed by at least one processor of a wireless access terminalfor communicating with a base transceiver station of a radio network,cause the wireless access terminal to perform operations comprising:initiating a transition from a traffic state to an active hold state inresponse to absence of reverse link traffic during a first predeterminedtime period, initiating a transition from the active hold state to thetraffic state in response to presence of reverse link traffic,initiating a transition from the active hold state to the dormant statein response to absence of forward link traffic and reverse link trafficduring at least a second predetermined period, initiating a transitionfrom the dormant state to the traffic state in response to presence ofreverse link traffic, after transitioning into the active hold state,remaining in the active hold state during simultaneous presence offorward link traffic and absence of reverse link traffic, and in theactive hold state, powering off at least one component of thetransmitter so that duty cycle of said at least one component is lessthan twenty-five percent in the active hold state.
 11. Themachine-readable medium of claim 10, wherein the instructions, whenexecuted by said at least one processor, further cause the wirelessaccess terminal to perform operations comprising: powering on said atleast one component of the transmitter for at least a majority of timein the traffic state.
 12. The machine-readable medium of claim 11,wherein the instructions, when executed by said at least one processor,further cause the wireless access terminal to perform operationscomprising: providing feedback to the base transceiver station in theactive hold state, the step of providing feedback in the active holdstate being performed with a first frequency; and providing feedback tothe base transceiver station in the traffic state, the step of providingfeedback in the traffic state being performed with a second frequency,the second frequency being greater than the first frequency.
 13. Themachine-readable medium of claim 12, wherein the feedback comprisesreverse link pilot and rate control.
 14. The machine-readable medium ofclaim 10, wherein the instructions, when executed by said at least oneprocessor, further cause the wireless access terminal to performoperations comprising: transitioning from the dormant state to theactive hold state in response to simultaneous presence of forward linktraffic and absence of reverse link traffic.
 15. A wireless accessterminal for communicating with a base transceiver station of a radionetwork, the wireless access terminal comprising: a means for receivingforward link transmissions from the base transceiver station; a meansfor sending reverse link transmissions to the base transceiver station;a means for storing program code; and a controller means for executingthe program code to cause the wireless access terminal to perform stepscomprising: initiating a transition from a traffic state to an activehold state in response to absence of reverse link traffic during a firstpredetermined time period, initiating a transition from the active holdstate to the traffic state in response to presence of reverse linktraffic, initiating a transition from the active hold state to a dormantstate in response to absence of forward link traffic and reverse linktraffic during at least a second predetermined period, initiating atransition from the dormant state to the traffic state in response topresence of reverse link traffic, after transitioning into the activehold state, remaining in the active hold state during simultaneouspresence of forward link traffic and absence of reverse link traffic,and powering off at least one component of the transmitter so that dutycycle of said at least one component is less than twenty-five percent inthe active hold state.
 16. A method of operating a wireless accessterminal for communicating with a base transceiver station of a radionetwork, the method comprising: initiating a transition from a trafficstate to an active hold state in response to absence of reverse linktraffic between the wireless access terminal and the base transceiverstation during a first predetermined time period, initiating atransition from the active hold state to the traffic state in responseto presence of reverse link traffic between the wireless access terminaland the base transceiver station, initiating a transition from theactive hold state to the dormant state in response to absence of forwardlink traffic and reverse link traffic between the wireless accessterminal and the base transceiver station during at least a secondpredetermined period, initiating a transition from the dormant state tothe traffic state in response to presence of reverse link trafficbetween the wireless access terminal and the base transceiver station,after transitioning into the active hold state, causing the wirelessaccess terminal to remain in the active hold state during simultaneouspresence of forward link traffic and absence of reverse link trafficbetween the wireless access terminal and the base transceiver station,and in the active hold state, powering off at least one component of atransmit chain of the wireless access terminal so that duty cycle ofsaid at least one component is less than a predefined duty cyclethreshold in the active hold state.
 17. The method of claim 16, whereinthe predefined duty cycle threshold is twenty-five percent.
 18. Themethod of claim 17, further comprising: causing the wireless accessterminal to power on said at least one component of the transmitter forat least a majority of time in the traffic state.
 19. The method ofclaim 18, further comprising: providing feedback from the wirelessaccess terminal to the base transceiver station in the active holdstate, the step of providing feedback in the active hold state beingperformed with a first frequency; and providing the feedback from thewireless access terminal to the base transceiver station in the trafficstate, the step of providing feedback in the traffic state beingperformed with a second frequency, the second frequency being greaterthan the first frequency.
 20. The method of claim 19, wherein the secondfrequency is at least twice the first frequency.
 21. The method of claim19, wherein the second frequency is at least four times the firstfrequency.
 22. The method of claim 19, wherein the second frequency isabout 150 Hertz, and the first frequency is about 75 Hertz.
 23. Themethod of claim 19, wherein the second frequency is about 150 Hertz, andthe first frequency is about 37.5 Hertz.
 24. The method of claim 19,wherein the feedback comprises reverse link pilot and rate control. 25.The method of claim 19, wherein the feedback comprises data rate control(DRC).
 26. The method of claim 19, wherein the feedback comprises datasource control (DSC).
 27. The method of claim 18, further comprising:providing feedback from the wireless access terminal to the basetransceiver station once in eight slots in the active hold state; andproviding feedback from the wireless access terminal to the basetransceiver station once in four slots in the traffic state.
 28. Themethod of claim 18, further comprising: providing feedback from thewireless access terminal to the base transceiver station once in sixteenslots in the active hold state; and providing feedback from the wirelessaccess terminal to the base transceiver station once in four slots inthe traffic state.
 29. The method of claim 17, further comprising:causing the wireless access terminal to transition from the dormantstate to the active hold state in response to simultaneous presence offorward link traffic and absence of reverse link traffic.
 30. The methodof claim 17, wherein the step of initiating the transition from thetraffic state to the active hold state comprises sending a spare reverserate indicator (RRI) codeword to the base transceiver station.
 31. Themethod of claim 30, further comprising: receiving from the basetransceiver station an acknowledgement of the spare RRI codeword; andtransitioning the wireless access terminal to the active hold state inresponse to the acknowledgement.
 32. A method of operating a wirelessaccess terminal for communicating with a base transceiver station of aradio network through a forward link and a reverse link, the methodcomprising: step for causing the wireless access terminal to enter adormant state in response to a period of traffic inactivity on theforward and reverse links between the wireless access terminal and thebase transceiver station; step for causing the wireless access device toenter a traffic state in response to traffic activity on the reverselink; and step for causing the wireless access terminal to enter anactive hold state in response to a period of traffic inactivity on thereverse links, the step for causing the wireless access terminal toenter the active hold state being performed regardless of trafficactivity on the forward link, wherein the wireless access terminal inthe active hold state powers on and off at least a portion of a transmitchain of the wireless access terminal with a duty cycle smaller thantwenty-five percent.
 33. A base transceiver station in a radio network,the base transceiver station comprising: a receiver configured toreceive data from a wireless access terminal on a reverse link; atransmitter configured to transmit data to the wireless access terminalon a forward link; and a processor coupled to the receiver and to thetransmitter, wherein the processor is configured to cause the basetransceiver station to perform steps comprising: granting a request fromthe wireless access terminal to enter an active hold state, wherein thewireless access terminal generates the request in response to a periodof traffic inactivity on the reverse link, and wherein the wirelessaccess terminal decreases feedback update frequency for the forward linkin the active hold state relative to a traffic state, transmittingforward link traffic while the wireless access terminal is in the activehold state, and receiving reverse link traffic in the traffic state. 34.The base transceiver station of claim 33, wherein the processor isfurther configured to cause the base transceiver station to vary powercontrol set point of the wireless access terminal depending on state ofthe wireless access terminal, wherein the power control set point ishigher in the active hold state than in the traffic state for the samesignal to interference and noise ratio (SINR).
 35. The base transceiverstation of claim 33, wherein the processor is further configured tocause the base transceiver station to increase power control set pointof the wireless access terminal when the wireless access terminal is inthe active hold state and the power control set point is below apredetermined power limit.
 36. The base transceiver station of claim 33,wherein the processor is further configured to cause the basetransceiver station to vary power control set point of the wirelessaccess terminal depending on the feedback update frequency.
 37. A basetransceiver station in a radio network, the base transceiver stationcomprising: a means for receiving data from a wireless access terminalon a reverse link; a means for transmitting data to the wireless accessterminal on a forward link; and a control means for processing, thecontrol means being coupled to the receiver and to the transmitter,wherein the control means is configured to cause the base transceiverstation to perform steps comprising: granting a request from thewireless access terminal to enter an active hold state, wherein thewireless access terminal generates the request in response to a periodof traffic inactivity on the reverse link, and wherein the wirelessaccess terminal decreases feedback update frequency for the forward linkwhile in the active hold state relative to a traffic state, andtransmitting forward link traffic while the wireless access terminal isin the active hold state.
 38. A method of operating a base transceiverstation in a radio network to control a wireless access terminal, themethod comprising: granting a request from the wireless access terminalto enter an active hold state, wherein the wireless access terminalgenerates the request in response to a period of traffic inactivity on areverse link between the wireless access terminal and the basetransceiver station, wherein the wireless access terminal in the activehold state provides feedback for a forward link between the wirelessaccess terminal and the base transceiver station with a first frequency,and wherein the wireless access terminal provides feedback for theforward link in a traffic state with a second frequency, the secondfrequency being greater than the first frequency; and transmittingtraffic on the forward link while the wireless access terminal is in theactive hold state.
 39. A machine-readable medium comprisinginstructions, the instructions, when executed by at least one processorof a base transceiver station of a radio network, cause the basetransceiver station to perform operations comprising: granting a requestfrom a wireless access terminal to enter an active hold state, whereinthe wireless access terminal generates the request in response to aperiod of traffic inactivity on a reverse link between the wirelessaccess terminal and the base transceiver station, wherein the wirelessaccess terminal in the active hold state provides feedback for a forwardlink between the wireless access terminal and the base transceiverstation with a first frequency, an wherein the wireless access terminalprovides feedback for the forward link in a traffic state with a secondfrequency, the second frequency being greater than the first frequency;and transmitting traffic on the forward link while the wireless accessterminal is in the active hold state.